Frequently asked questions.

Frequently asked questions.

What is a meltblown die?

As we all know, the melt-blown cloth is the “heart” of masks, so melt-blown cloth mold is also used to produce melt-blown cloth mold, also known as melt-blown cloth nozzle or spinneret in the industry.

Melt blown cloth mold is made of yk30 (SK3) carbon tool steel, tungsten carbide, and other steel. For the die head of melt-blown cloth, the micro-hole diameter is very small, mostly 0.1-0.3mm, with a spacing of 0.6-0.7mm. For example, a 550mm die has nearly 1000 holes, and the perpendicularity of 0.2mm is the key. Laser drilling has high precision.

Design drawing of melt blown fabric

Design drawing of melt-blown fabric

Most of the die heads are rectangular spinnerets, which are made of SUS316L, SUS304, SUS630, SUS431 and other stainless steel.

In the past, in order to ensure the concentricity of the spinneret micro-hole and pilot hole, it was generally processed from one side, from macropore to micropore. Because of the great overhanging depth, the difficulty coefficient is very high. Due to the urgent need of rapid production, most of the process has been changed to micro-hole processing from the back, but this will produce concentricity, burr and other problems.

After using YFG abrasive flow to solve the problems of burr and hole plugging, polishing and cleaning can be carried out, and the machine can be put into use. In the production of melt-blown fabric, the wire is sprayed through the spinneret of melt-blown fabric mold. Meltblown fabric is the core material of the mask. Polypropylene is the main raw material of the melt-blown fabric. The fiber diameter can reach 1-5 microns.

In the spinneret module, there is a row of spinning micropores under the spinning melt pool, and the diameter of micropores is generally 0.3-0.4 mm. In order to be more conducive to spinning forming, the aspect ratio is much larger than that of conventional melt spinning, which is generally 10-15. At the same time, a special air cavity is formed between the spinneret assembly and the air knife. The high-pressure hot air flows through the narrow slot of the air cavity at a speed similar to the speed of sound. A spinning tap is formed between the blade of the air knife and the tip of the spinneret assembly.

The melt is ejected from the spinning micropores and is clamped by high-speed airflow at the spinning cone, and then stretched to form ultrafine fibers after cooling.